The present invention relates to an antiskid apparatus for automotive vehicles.
An example of a conventional antiskid apparatus for automotive vehicles is disclosed in the specification of Japanese Patent Publication (KOKOKU) No. 49-28307.
As shown in FIG. 2, the conventional antiskid apparatus has an inlet solenoid valve 3 arranged between a master cylinder 1 and a wheel brake 2, and an outlet solenoid valve 5 arranged between the wheel brake 2 and a reservoir 4. A pump 6 is arranged between the reservoir 4 and the master cylinder 1 and the circuit arrangement is such that a working fluid discharged from the pump 6 circulates to the master cylinder 1 and the inlet solenoid 3.
In the above-described conventional antiskid apparatus, antiskid control is carried out by switching the inlet solenoid valve 3 and outlet solenoid valve 5. However, in accordance with control based solely on switching of the solenoid valves 3 and 5, a decrease in pressure in the wheel brake 2 takes place slowly and response is poor when the vehicle is traveling on a road surface having a low coefficient of friction .mu., even though the inlet solenoid valve 3 is closed and the outlet solenoid valve 5 is open. Conversely, when there is an increase in the pressure, it is desired that the pressure increase take place slowly in order to avoid sudden braking. However, since pump discharge fluid is connected directly to a point of the line between the master cylinder 1 and inlet solenoid valve 3, wheel brake pressure undergoes a violent increase. As a result, wheel lock-up tends to occur and it becomes difficult to carry out antiskid control.